Robert Kirkman's post-apocalyptic zombie thriller "The Walking Dead" is a hugely popular and acclaimed entertainment franchise.

The television show's most recent season averaged 18.4 million viewers per episode (including DVR views and re-runs in the first week), according to AMC. The award-winning, monthly comic book series, which the TV show is based on, is consistently a top seller.

In addition to being the executive producer of "The Walking Dead" show and the writer of the comic, Kirkman writes the superhero comic "Invincible" and his spin on the exorcism genre, "Outcast."

He's also developing a "Walking Dead" spinoff for television, an "Outcast" TV show, and his first film, "Air," which is scheduled to be released next year by Sony Pictures Worldwide. All of these projects are housed under his growing company, Skybound Entertainment.

He tells Business Insider that he's able to balance all of these projects by always having an outlet for his ideas, staying focused, setting difficult deadlines, and keeping things interesting for himself.

Here are the fundamentals of his creative process:

He avoids multitasking and doesn't let his ideas drift away.

Kirkman says that sometimes he doesn't even know how he keeps so many characters and plotlines floating around in his head, but that it helps that he only focuses on one of his titles at a time and always takes extensive notes.

"I have a notepad in my phone that I'm always pulling out when I'm pretty much anywhere," Kirkman says. He'll jot down a line of dialogue or a scene if it comes to him.

Since the "Walking Dead" show and comic have significant discrepancies, he treats them like two entirely different projects.

Kirkman explains what it's like to juggle the two versions of Rick Grimes, the series' protagonist:

The Rick Grimes that's in the show, he hasn't quite developed to the point that the Rick in the comic book has. He eventually will, but by the time he does that, the Rick in the comic book will be completely different and on another track — or he'll be dead. If there's ever a case where I go, "Oh, that would be a really cool thing to do with Rick," okay, now I need to decide if that's going to go into the comic or the show.

He plans years into the future.

Kirkman ensures that he'll never run out of ideas by creating "road maps" for each of his series.

He's got a five- or six-page road map for "The Walking Dead" comic series, for example. This document is filled with blocks of one or two paragraphs representing 20-50 issues — that means a couple quick paragraphs can represent four years' worth of storyline.

Kirkman says he'll update this roadmap two to five times a year, but doesn't spend too much time working out the details.

"Looking at the past of the comic, that document at some point would've said, you know, 'Live in a prison for awhile,' 'Encounter Woodbury,' and 'Fight a guy called The Governor.' That is enough to remind me of all the other stuff I was thinking of," he says.

He adds that everything is subject to change, but the road maps keep him from taking on more than he can handle. Before "Outcast" launched last month, he developed it for three years.

He sets unrealistic deadlines for himself.

"I kind of thrive in chaos," Kirkman says. He likes to maintain this feeling of urgency by giving himself "completely and utterly unrealistic goals."

He explains:

I'll be like "I want to write 12 pages today," but I really only need to write like four or five. But if I try to write 12, I might write six or seven. What that does though, is it gives me a crushing sense of failure at the end of every day. So I'm like, "Oh my God, I didn't get those 12 pages done. I suck! What is wrong with me?" and the next day I work harder because I have to make up for that unrealistic deadline I didn't make. And so it's probably not too good for my psyche, but as far as productivity goes, it seems to help.

A typical comic issue takes anywhere from two to seven days to write Kirkman says, depending on how much time is available. But if it takes him longer than a week to finish, the work goes from being fun to being a chore.

He focuses on his work, not his success.

Kirkman has been writing comics for the past 14 years, but his work entered the mainstream when "The Walking Dead" TV show launched in 2010 and quickly became a hit.

"If I actually sat and considered the number of people that are looking 'The Walking Dead' and scrutinizing 'The Walking Dead' at this point, I would probably get a little nervous, get stage fright, and have trouble writing. But when I'm doing my thing, I pretty much ignore the fact that it has grown into this enormous, worldwide thing," Kirkman says.

He uses the success of his television show to open up new opportunities he otherwise would not have had, he explains, but he does everything he can to keep the weight of an increasingly larger audience from affecting his work.

He embraces others' creativity.

Kirkman writes his comics' scripts, but lets his artists use their unique styles to bring his stories to life. He says he also refrains from being overprotective of his work when he adapts the "Walking Dead" comic into the TV show, even though he has complete control of the "Walking Dead" intellectual property.

He sits in the writers' room for the show "pretty much full time from January to June" before the season goes into production. He enjoys the opportunity to tell a new story.

"I don't really sit back in my chair and say, 'No, not that!' We're all in it together, and I look at us as equals when we're working on the show," he says.

He always has new projects to work on.

"If I'm not working on something new, I just don't feel good about what I'm doing," Kirkman says.

In addition to his comics, shows, and movie, he says he's also thinking about and taking notes on "a couple of other projects that probably won't see the light of day for another four or five years."

Right now, he's got enough to keep him from getting bored.

"I'm pretty much at my capacity right now, but I'll figure out how to do something new at some point," he tells us.

See Also:

Former SpaceX Employee Explains What It's Like To Work For Elon MuskTim Ferriss Uses This Simple Productivity Hack To Organize His Days'It Just Takes Your Breath Away': What It's Like To Step Into Space For The First Time

SEE ALSO: 'Game Of Thrones' Creator George R.R. Martin Shares His Creative Process